FIG. 1 shows a diagrammatical view of the construction of a prior art synthesizer equipped with a rhythm accompaniment apparatus comprising a keyboard 10, a rhythm pattern selector 20, a control section 30, a sound source unit 40 and an amplifier-speaker system 50.
The control section 30 is composed by a so-called microcomputer. As is commonly known, the microcomputer comprises a central processing unit (hereinafter referred to as "CPU") 31, a ROM 32 storing a program for operating the CPU 31 in a predetermined sequence, a RAM 33 used to temporarily store the data input from the keyboard 10 or the rhythm pattern selector 20 and the operational results, an input port 35 and an output port 36. Since the control section 30 in the illustrated example is designed to control a synthesizer equipped with a rhythm accompaniment apparatus, the microcomputer has a rhythm pattern memory 34 added thereto so that rhythm pattern data may be output.
The keyboard 10 and rhythm pattern selector 20 are connected with the input port 35 which in turn inputs the keyboard information and rhythm pattern selection information to the control section 30. The keyboard information is taken through the input port 35 into the CPU 31 at a timing allocated to the position of the associated key as by a key scan signal. In the CPU 31 the keyboard information is decoded and translated to a key code signal which is then input through s bus line 37 and the output port 36 to a keyboard sound source 41 where a musical sound signal having a frequency and a selected and preset tone corresponding to the depressed key is D/A converted to generate an analog signal. The analog musical sound signal output from the sound source unit 40 is then input to an amplifier-speaker system 50 which comprises a mixer 51, an amplifier 52 and a speaker 53 and converts the musical signal to produce a musical sound.
In the rhythm pattern selector 20 on the other hand, a rhythm pattern suitable for any desired type of music such as rock, swing, jazz, waltz, etc. is selected and preset, and a code representing the preset rhythm pattern is input to the CPU 31. The CPU 31 reads the storage region of a rhythm pattern selected from the rhythm pattern memory 34 and outputs the rhythm pattern data through the output port 36 to the accompaniment sound source 42 to generate a sound for rhythm accompaniment.
The accompaniment sound source 42 includes a sound source circuit for generating sounds of various types of musical instruments used for rhythm accompaniment. Sounds of rhythm accompaniment instruments include mainly those of percussion instruments such as snare drums, rim shots, open hi-hats, closed hi-hats, ride cymbals, crash cymbals, etc. Each of the rhythm patterns is predetermined with respect to a particular combination of percussion instruments and the rhythm pattern of the sounds of the respective percussion instruments and is stored in the rhythm pattern memory 34. Upon selecting a particular rhythm pattern, the rhythm pattern data of the associated percussion instruments are transmitted to the accompaniment sound source 42 where they are converted to signals of the sounds of the percussion instruments in the selected combination and are output to the amplifier-speaker system 50.
The rhythm pattern data stored in the rhythm pattern memory 34 are composed of sound data for designating the type of percussion sounds to be generated and the set of timing data to generate the percussion sounds. As a matter of convenience, the same key codes as some of the key codes allocated to the keys of the keyboard 10 are employed as the percussion sound data and the type of percussion sounds is designated by the key codes. Discrimination between the key codes used for the accompaniment information and the key codes for the keyboard keys is effected by the transmitting timings.
As indicated above, in the conventional automatic rhythm accompaniment producing apparatus, the rhythm pattern memory 34 has only one combination of percussion instruments suitable for each of the rhythm patterns stored therein. Accordingly, it has the disadvantage that the accompaniment cannot be subtly varied within the same musical piece. If the rhythm accompaniment is to be altered between gentle and intense sections in the same musical piece, the rhythm accompaniment itself must be selected again. On this account, it would be convenient in a musical performance to provide a number of different rhythm pattern data involving combinations of percussion instruments having some of the instruments replaced with others for various types of music. However, the provision of many different rhythm pattern data having different combinations of percussion instruments would undesirably cause an excessive increase in the memory capacity of the rhythm pattern memory 34, resulting in an increase in cost.